join in something—associate with other people in an activity, especially when they are already engaged in it:
- As I stood with people talking about insignificant things, my small daughter joined in the conversation.
join something—
1. become a member of a party, club, organization, etc.:
- Many well-known figures joined the party at this time, including Pablo Picasso.
2. = join in something:
- Suddenly the mood changed completely and a third person joined the conversation, interested in where we were going.